Prevalence of Powassan Virus in Ixodes scapularis in Northern Wisconsin

Link: http://www.ajtmh.org/cgi/content/full/79/6/971

Excerpt:

These findings suggest that deer tick-borne POWV may present a public health risk to human residents of and visitors to infested sites. 
Paradoxically, despite the apparent increase in the incidence of human infection, the proportion of ticks infected remained constant between the 1990s and the present. 
The increased geographic distribution of deer ticks and concomitant increases in their populations might produce a greater number of infected ticks overall, or might facilitate spillover from cryptic enzootic foci, which might produce additional human POWV infections. 

It may be that a proportion of the recent increase in the recognition of POWV encephalitis in North America is attributable to the emergence of DTV. 
Ongoing studies will therefore more completely characterize the transmission cycle and molecular epidemiology of DTV within this focus. 

Importantly, infection by viruses within the TBE serologic complex results in a wide range of clinical outcomes, ranging from asymptomatic to severe: DTV may be less pathogenic than prototypical POWV, as has been suggested previously. 

Experimental studies are required to evaluate this hypothesis. In the absence of this data, clinicians should consider tick-borne flavivirus infection in patients presenting 1) with neurologic symptoms and 2) residence or travel to tick-infested sites.